Avaliação do potencial aurífero nos sedimentos aluviais no vale do Rio Poti

Abstract

Gold, known for its value and status in society, is a mineral asset that in its history had the exploration in alluvial sedimentary systems as a pioneer due to its ease of extraction. With the evidence of pan concentrates in the Rio Poti, which begins in the state of Ceará and flows to Piauí, the possibility of a gold -bearing potential in this region was glimpsed. For this, an area about 60 kilometers west of the city of Crateús - CE was delimited with the objective of evaluating this potential and the possible models of gold occurrence. For this purpose, samples were collected both from the paleoterrace of the river and from the river active course, in the first stage there were eight samples and in the second six, which were analyzed in the laboratory. From the first point in Ceará to the last, in the state of Piauí, gold was identified in practically every route, of approximately 35 km long. Geologically, the area is located on the border of two large provinces, the Borborema Province in the eastern portion, and the Parnaíba Province (Parnaíba Basin) in the central -western portion. The first, Borborema Province can be a source of gold and Parnaiba can be the region of accumulation of this mineral due to drainage and erosion of crystalline rocks accumulating in alluvial sediments. This study shows that gold is pure and that its grain size varies from 100 to 600 microns and may have particles of up to 1 mm. The occurrence is better on the paleoterrace than on the river active course. Associated with the imaging, it was possible to delimit different sedimentation conditions, considering the edges of the valley with conglomeratic paleoterraces and sandy -clay matrix and in the active bed sandstones and conglomerates with sandy matrix.